Abstract:

Karman vortex phenomenon near downstream side of a group of hydro turbine flow passage components with same outlet edge thickness and different outlet edge angle is simulated, by using numerical simulation method. Influence of outlet edge angle on Karman vortex frequency is studied. The results show that Karman vortex frequency decreases with an increasing outlet edge angle. Karman vortex frequency obtained by numerical simulation method decreased to one third as compared with the one obtained by using Karman vortex frequency theoretical formula for flow around circular cylinder, when outlet edge angle is increased to 30°. Based on the comparison between results of numerical simulation and values obtained by theoretical formula, and data processing, Relation curve and approximate linear fitting formula between Strouhal number outlet edge angle of flow passage components are obtained. By compared with the test data of Karman vortex vibration of stay vane outlet edge of an hydro turbine, accuracy of Karman vortex numerical simulation method for hydro turbine flow passage components is validated, and Strouhal number calculation formula is also validated. The research shows great significance in optimal shape design of outlet edge of hydro turbine flow passage components and avoiding vibration induced by Karman vortex.

Key words: flow passage components, Karman vortex frequency, outlet edge angle, hydro turbine